The power source of a typical drone is a battery. The flight time of the drone depends on the capacity of the battery. However, the capacity of the battery is limited, and when the drone requires a longer flight time, the battery may have difficulty providing sufficient power. To extend the flight time of the drone, a tethered drone is another option. A ground device may provide power to the tethered drone through a power cable, and therefore the flight time of the tethered drone may be significantly extended.